A system on chip (SoC) is a type of integrated circuit (IC) device that integrates all components of a computer or other electronic system into a single chip. An SoC may contain digital, analog, mixed-signal, and often radio-frequency functional circuitry, all fabricated on a single chip substrate. Each SoC typically includes one or more phase-locked loop (PLL) circuits to generate clock signals used to synchronize operations and communications of the various functional circuits. In addition, each SoC typically includes from one to thousands of “embedded” memory circuits that store data utilized by the system's functional circuits. Processors and microcontrollers are examples of two other types of IC devices that include PLLs and embedded memory.
It is important to make sure that certain signals (e.g., data read from embedded memory, the clock signals generated by PLLs, etc.) are generated according to specifications in order to ensure reliable operation of an SoC (or other IC) device. Embedded memory performance is one of the critical characteristics affecting overall reliability of an SoC/IC device. Especially in the adaptive systems or automotive chips, it is important to make sure embedded memory is performing per specifications under the changing conditions of voltage and temperature. Embedded memory access time which is the delay from memory clock to the output data during memory read operation is an important parameter that determines the performance of memory and it always was a difficult task to accurately characterize it since the actual delays of high performance memories usually are within only few hundreds of picoseconds range. Prior art on measuring memory delay is based on using delay cells and applying extensive calibration to achieve acceptable accuracy.
What is needed is a simple, reliable and cost-effective test circuit and method for accurately measuring and analyzing operating characteristics of embedded memory and periodic signals generated on an SoC (or other IC) devices that avoids the problems associated with conventional approaches.